Textile adhesive from polyurethane containing carboxylate groups

ABSTRACT

AQUEOUS ADHESIVE COMPOSITION CONTAINING A DISPERSED POLYURETHANE POLYMER, THE METHOD OF USING THE ADHESIVE COMPOSITION IN TEXTILE APPLICATIONS, AND THE TEXTILE MATERIALS THUS OBTAINED. THE ADHESIVE COMPOSITION IS AN AQUEOUS DISPERSION OF A PARTICULAR CLASS OF SELF-DISPERSIBLE OR EMULFIFIABLE POLYURETHANE POLYMERS. THE AQUEOUS DISPERSIONS ARE OBTAINED BY ADDING A PARTICULAR CLASS OF ISOCYANATE-TERMINATED POLYURETHANE PREPOLYMERS HAVING PENDANT ARBOXYL GROUPS TO WATER CONTAINING A TERTIARY ALIPHATIC AMINE AND ALLOWING CHAIN EXTENSION WITH WATER TO PROCEED UNTIL ALL OF THE ISOCYANATE GROUPS HAVE BEN REACTED. THE RESULTING POLYURETHANE LATEX IS THICKENED TO THE DESIRABLE VISCOSITY WITH SUITABLE THICKENING AGENTS.

United States Patent ()ifice 3,640,924 Patented Feb. 8, 1972 3,640,924TEXTILE ADHESIVE FROM POLYURETHANE CONTAINING CARBOXYLATE GROUPS DavidTrimble Hermann, Flemington, and Kenneth Herald llemley, WarrenTownship, Somerset County, N.J., asslgnors to American Cyan-amidCompany, Staniford, Conn. No Drawing. Filed Dec. 20, 1968, Ser. No.785,779 Int. Cl. C08g 22/16, 41/00 U.S. Cl. 26013 3 Claims ABSTRACT OFTHE DISCLOSURE Aqueous adhesive compositions containing a dispersedpolyurethane polymer, the method of using the adhesive composition intextile applications, and the textile materials thus obtained.

The adhesive composition is an aqueous dispersion of a particular classof self-dispersible or emulsifiable polyurethane polymers. The aqueousdispersions are obtained by adding a particular class ofisocyanate-terminated polyurethane prepolymers having pendant carboxylgroups to water containing a tertiary aliphatic amine and allowing chainextension with Water to proceed until all of the isocyanate groups havebeen reacted. The resulting polyurethane latex is thickened to thedesirable viscosity with suitable thickening agents.

This invention relates to textile adhesive compositions.

More particularly, it relates to aqueous adhesive compositionscontaining a dispersed polyurethane polymer, to the method of using theadhesive composition in textile applications and to the textilematerials thus obtained.

Large amounts of adhesives are used in the textile field, particularlyin the laminating and flocking arts. Laminating involves the bonding offabrics, both synthetic and natural, either to one another or to otherplastic materials to form a multilayer product. Flocking involves thebonding of short, cut fibers in a perpendicular position to a substrateto form a pile-like material.

Flocked fabrics are assuming an increasingly important place in thetextile and related industries. These pilelike materials aremanufactured, in general, by coating a substrate with an adhesive andthen embedding the ends of short, cut fibers in the adhesive. Thethickly arranged cut fibers are oriented vertically to the substrate byvarious means. Suede-, feltand velvet-like fabrics are obtained with theshortest fibers and rug and carpet materials and fur-like materials withlonger fibers. The flocked fabrics find a wide variety of uses includingautomotive carpets, linings, window channels and weather strippings,simulated suede eflects, design flocking of draperies and similarfabrics, floor coverings, wall coverings, paint rollers, etc.

Substrates have included a variety of woven and nonwoven fibrousmaterials and polymeric sheets, films and foams. Lamination allows theattachment of flocked webs or films to another substrate. Representativesubstrate materials are cotton, jute, polyester (Dacron), polyvinylchloride, polyurethane, polyethylene, polystyrene, etc.

A variety of cut fibers or flock, both in the tow and staple forms, areavailable. They include viscose rayon, nylon, polyester and polyacrylic,in addition to cotton, wool and cellulose acetate.

Various methods are used for coating and orienting the cut fibers orflock with respect to the substrate. Two of the most important aremechanical vibration, as by the beater-bar system, and electrostaticprocedures.

The three factors which primarily determine the quality and wearingproperties of a flocked product are adhesives, flock and coatingtechnique. For flocking, adhesives must meet several requirements. Forexample, floor coverings require good anchoring of the coating to theface, excellent adhesion of the pile and highest wearing and scrapingresistance in the dry and wet state. Also, the fibers must be fixed inthe vertical position with highest durability. The following propertiesof the adhesive are also important: the rheological properties, theconductivity and sometimes the dielectric constant (particularly forelectrostatic flocking), the surface tension to the base and flockmaterial, the nature of the solvents and their evaporative speed, theviscosity-temperature behavior, etc. In addition to securely adheringthe flock to the substrate, the adhesive must be curable under desirableand economical conditions, and the cured adhesive must be durable toexposure to solvent, weather, etc. In the apparel field, resistance todry-cleaning and/or laundering is particularly important.

As indicated above, laminating in the textile field means the bonding ofa fabric to the same or different fabric or fabrics or the bonding ofone or more fabrics to plastics materials, including films, sheetingsand foams.

The fabrics used in laminating may be woven, 'knitted or nonwoven. Theymay contain a wide variety of fabrics, both natural and synthetic,including cotton, rayon, linen, wool, silk, polyester, nylon, celluloseacetate, acrylic, modacrylic, etc., and mixtures thereof.

The plastics materials used in laminating are of a wide variety. Theplastics are normally limited to thermoplastic polymers, includingpoly(vinyl chloride), poly(vinyl acetate), cellulose esters such ascellulose acetate and cellulose acetate-butyrate, poly(-vinyl butyral),polyethylene, polypropylene, polyurethane, polyamide, polyesters, etc.This wide variety of plastics materials will not necessarily be found inall forms, i.e., film, sheeting and foams. Film and sheeting are largelymade of poly(viny1 chloride), although other plastics are extensivelyused, as well known in the art. The foams are usually made of poly(vinylchloride) or a polyurethane, but other polymers, such as polyamides, mayalso be used.

The laminated textile materials are used in many fields, includingapparel, home furnishings and automotive uses. The following specificuses are representative. Suit and coat materials having a laminatedlining, possibly with a foam interlining, are popular. Laminatedsynthetic leathers are used in upholstery, handbags, footwear, etc. Atypical foamed vinyl synthetic leather is composed of three layers, 1) atextile backing cloth, (2) an expanded (foamed) poly(-vinyl chloride)middle layer and (3) a poly(vinyl chloride) sheeting as the top layer.

The adhesives used in textile laminating should provide products having(1) dimensional stability to washing, dry cleaning and pressing, (2)durability of the bond between two components to washing, dry cleaningand pressing and (3) satisfactory handle and drape characteristics.Furthermore, the adhesive composition must be applicable by theconventional methods for applying adhesive to fabrics or plasticsmaterials, as by doctor blade technique using a plain or gravuretransfer roll. The adhesive should be sufficiently viscous to preventpenetration into the fabric or foam. It should be flexible, even whenfully cured, and should not age. Although many of the adhesivescurrently used have a solvent base, aqueous base adhesives are desirablesince 1) they can be diluted with Water for cleaning purposes, (2) theydo not present a fire or explosion hazard, and (3) they have less odorand are nontoxic.

It is therefore an object of this invention to provide an aqueousadhesive composition for general textile bonding purposes, butparticularly for laminating and flocking utility. This and other objectsof the invention will become apparent as the description thereofproceeds.

An aqueous adhesive composition has now been discovered which iseminently useful as a textile bonding adhesive, particularly for bondingfabric-to-fabric and laminating fabric-to-foamed plastic material. It isuseful in other textile bonding applications, such as textile flocking.It is also of value as a binder for nonwoven fabrics, and it may be usedas a textile finishing agent ,such as a hand modifier, awrinkle-recovery enhancer or a tear and tensile strength improver forwoven and knitted fabrics.

The adhesive composition of this invention is an aqueous dispersion of aparticular class of self-dispersible or emulsifiable polyurethanepolymers. The aqueous dispersions are obtained by adding a particularclass of isocyanate-terminated polyurethane prepolymers having pendantcarboxyl groups to water containing a tertiary aliphatic amine andallowing chain extension with water to proceed until all of theisocyanate groups have been reacted. The resulting polyurethane latex isthickened to the desirable viscosity with suitable thickening agents.

The isocyanate-terminated polyurethane prepolymers having pendantcarboxyl groups are prepared by reacting an organic diisocyanate with amolecular deficiency of a mixture of two types of glycol.

The first type of glycol is a non-polymeric glycol containing a pendantcarboxyl group and the second type is a conventional polyalkylene etherglycol, or mixtures of such polyalkylene ether glycols.

The organic diisocyanate is an aromatic diisocyanate having theisocyanate groups directly attached to the aromatic ring, such as thetolylene diisocyanates, including 2,4- and 2,6-tolylene diisocyanateanclmixtures thereof; methylenebis (4-phenyl isocyanate); p-phenylenediisocyanate; 1,5-naphthylene diisocyanate, and the like. Thediisocyanates may contain other substituent groups, such as halo,although those free of such groups are preferred.

The nonpolymeric glycol containing a pendant carboxyl group has theformula:

where R is hydrogen or a hydrocarbon radical, preferably lower alkyl(1-3 carbon atoms). The glycols of Formula I are for example2,2-bis(hydroxymethyl) lower alkanoic acids and they include2,2-bis(hydroxymethyl)acetic acid, 2,2-bis(hydroxmethyl)propionic,2,2-bis(hydroxymethyl) butyric acid, and 2,2-bis (hydroxymethyl)valericacid. The preferred glycol is 2,2-bis(hydroxymethyl)propionic acid.

The polyalkylene ether glycol has the formula:

H(OCHCHz) -OH wherein R is lower alkyl and q is an integer suflicientlylarge to provide an average molecular weight for the glycol of at least750, and up to 5,000, with a preferred average molecular weight range ofabout 1,700 to about 2,400. Representative glycols include polyethyleneether glycol, poly-1,2-propylene ether glycol, poly-1,2-butylene etherglycol, etc.

In preparing the prepolymer, at least 1.1 moles and up to about 5.0moles (preferably between 1.6 and 3.0 moles) of the diisocyanate permole of total glycol should be used. The molar ratio of nonpolymericglycol containing a pendant carboxyl group to the polyalkylene etherglycol should between about 0.25:1 to 2:1, preferably between 0.75:1 and1.25: 1. The temperature used for the reaction between diisocyanate andglycols should be between about 50 and 80 C.

The amount of water used with the prepolymer in forming thewater-extended polyurethane latex is not critical. Latices of solidscontent from about up to about 60% can be obtained, although a solidscontent of 50% is preferred. Formation of the latex at room temperatureis convenient and practical, although higher or lower temperatures maybe used.

The tertiary amine present in the water during the latex formation is atertiary lower alkylamine including trimethylamine, triethylarnine andtripropylamine, for example, preferably triethylarnine. The amount oftertiary amine used should be between 2% and 10%, preferably between 3%and 7%, based on weight of prepolymer.

Proper viscosity of adhesive is important to prevent undue penetrationof the adhesive into the substrate to which it is being applied. Inother words, the bulk of this adhesive should remain on the surface ofthe substrate to provide good adhesion. Viscosities in the order of20,000 to 100,000 cps. are normally satisfactory. Suitable thickeningagents are used to obtain the desired viscosity, and they include thosewell-known in the art such as methyl cellulose, hydroxyethyl cellulose,polyacrylic emulsion plus alkali, gurus, etc.

The adhesive of the invention can be used with any of the fabrics andplastic sheeting or foams normally used in the laminating processes,these include woven knit and non-woven fabrics of natural and syntheticfibers, and a variety of plastic sheeting and foams, but particularlythose made of poly(vinyl chloride) or polyurethane. In the flockingprocesses, the adhesive can be used with any of the substrates normallyused in the flocking process, including woven and non-woven fabrics ofnatural and synthetic fibers, paper, plastic coated fabrics, plasticfilms and sheets, wood, metal, rubber, glass, etc. Any of the flockingmaterials may be used. These include both synthetic and natural fibers.

The methods for applying the adhesive to the substrate are conventionaland any of the well-known procedures may be used. The assembling of thelaminate or flocked fabric is also by conventional procedures. Suchmethods are well-known in the art.

After the assembly step, it is necessary to dry and cure the adhesive.Drying and curing temperatures between 250 C. and 350 C., preferablybet-ween 270 C. and 325 C., are suitable.

The bonding obtained by the adhesive composition of this invention isvery durable. It has shown exceptional strength under wet conditions, asduring. and after laundering.

It appears that the exceptional durability of the adhesive bond towashing and drying may be depending on the breaking of the salt-form ofthe adhesive during the curing step with formation of the acid-form ofthe adhesive and free tertiary amine, the latter then volatilizing. Thismechanism may explain the necessity for proper selection of thenonpolymeric glycol containing a pendant carboxylic group and thetertiary amine. However, we do not wish to be bound by this theory.

Other agents may be added to the adhesive composition. For some uses itmay be desirable to add a thermosetting aminoplast precondensate, suchas melamine-formaldehyde and urea or urea-formaldehyde condensate, toimprove the solvent resistance of the adhesive. The preferred aminoplastprecondensates are melamine-formaldehyde condensates, including alkylethers thereof.

The following examples are set forth to illustrate the invention and arenot intended to be limitative.

EXAMPLE [I 8525 parts polypropylene glycol, of 2,000 m.w. was heated to50 C., and 418 parts of 2,2-bis (hydroxymethyl) propionic acid and 2864parts of tolylene diisocyanate (/20 mixture of 2,4- and 2,6-isomers)were slowly and uniformly added thereto. The mixture was heated at 70 C.for about 20 hours. The free NCO content of the prepolymer was about5.7%.

The prepolymer was added to a stirred solution of 316 parts oftriethylarnine in 22,200 parts of water at 5 C. to 10 C. The mixture wasstirred for about 8 hours at 20 C. to 30 C. The resulting emulsion wasabout 35% solids and to this there was added a dispersion of 2230 partsof Acrysol ASE-60 (commercial polyacrylic-type of thickening agent oftRohm & Haas) in 5820 parts of water. The adhesive composition, after 1to 2 hours of stirring, had a viscosity of about 60,000 cps. andcontained about 30% solids.

EXAMPLE II A swatch of woven wool fabric was placed on a flat surfaceand was covered with a perforated template. A portion of the adhesivecomposition of Example I was spread evenly and cleanly across thetemplate, thereby applying a pattern of small dots of adhesive to thewool. The template was removed and a swatch of cellulose acetate tricotwas placed on the wool. The two pieces of fabric were pressed togetherfor 30 seconds by the weight of a 7 inch by 10 inch by inch glass plate.The fabric assembly was then heated in an oven at 260 F. for 2 minutes.

The bonded fabric was cut into 1 inch strips. Two strips were placed inboiling water and stirring for 5 minutes and then in cool water. Peelstrength of the bond of the dry and wet strips was determined with aspring scale. On average, the peel strength of the wet strips was 72% ofthe peel strength of the dry strips.

Strips of the bonded fabric were also stirred in polychloroethylene forminutes. Peel strengths of the dry and wet strips were also determined.The peel strength of the wet strips was 54% of the dry strips.

This example illustrates the durability of the adhesive bond in bothaqueous and organic solutions, comparable to conventional laundering anddry cleaning conditions.

EXAMPLE III Using commercial equipment, a woven wool fabric wascontinuously coated with the adhesive composition of Example I, andcontacted with sheet polyurethane foam. The foam side of the thus formedlaminate was then coated with the adhesive and contacted with celluloseacetate tricot. The fabric-foam-fabric laminate was then heated bypassing it over a hot roller at about 375 F.

A firm, durably bonded laminated fabric was thus formed, having bondedstrength comparable to that described in Example II.

EXAMPLE IV The adhesive composition of Example I was applied by a knifecoater to cotton twill employing a 10-mil thickness of wet adhesive. Apolyacrylic iiock of 0.5 mm. length was sifted onto the wet adhesivewithin to seconds and the flock was then oriented by means of thebeater-bar technique. The flocked fabric was dried at 127 C. for 15minutes and the loose flock was removed by blowing with a stream of air.The flock was securely bonded to the substrate and had a soft,suede-like appearance and texture.

EXAMPLE V The laminating of Example II was repeated using the adhesiveof Example I to which was added 5% solids of aqueous solution, partiallymethylated (about 60%) trimethylol melamine, based on the polyurethanesolids in the adhesive composition.

The peel strength retention of the bonded fabric when wet withprechloroethylene was 61%, as determined by the procedure of Example II.

A comparison of the peel strengths of Examples II and V was as follows:

The peel strength of the bonded fabrics of Examples II and V weredetermined by taking a 1 inch strip of the bonded fabric, pulling thetwo fabrics apart at one end, fastening one fabric to a spring scale andpulling the other fabric until separation of the two fabrics took place.

TABLE I.-IEEL STRENGTH FOR EXAMPLES II AND V Example II Example V Dry,oz 19. 5 19. 5 Wet (water), oz 14 Wet (polychloroethylene), oz 10.5 12

While the present invention has been described in detail as to specificembodiments thereof, it is not intended that these details constituteundue limitations upon the scope of the invention, except insofar as thelimitations appear in the appended claims.

We claim:

1. A process for preparing a polyurethane adhesive composition in theform of an aqueous dispersion comprising the steps of:

(1) forming an isocyanate-terminated prepolymer by reacting to tolylenediisocyanate with a mixture of two glycols at a ratio of from 1.6 to 3.0moles of diisocyanate per mole of total glycol, one of said glycolsbeing a nonpolymeric glycol of the formula:

wherein -R is selected from the group consisting of hydrogen or loweralkyl, the other of said glycols being a polyalkylene ether glycol ofthe formula:

H(OCHCH2)QOH wherein R is lower alkyl and q is an integer sufficientlylarge to provide an average molecular weight of from 750 to 5000, themolar ratio of glycols being 0.25:1 to 2:1, respectively;

(2) forming a latex by reacting the isocyanate-terminated prepolymer inaqueous medium containing a tertiary lower alkylamine (C -C and allowingchain extension with water to proceed until substantially all of theisocyanate groups have been reacted; and

(3) adding a thickening agent to said latex to produce an adhesive ofviscosity in the range of from 20,000 to 100,000 cps.

2. The process of claim 1, wherein the tertiary lower alkylamine istriethylamine.

3. An adhesive composition as prepared by the process of claim 1. 1

References Cited UNITED STATES PATENTS 2,988,400 8/19'61 French 260-29.63,022,256 2/1962 Barnes et al. 2602.5 3,248,259 4/1966 Borsinello et al.117-139.5 3,438,940 4/ 1969 Keberle et al 26 0-67 3,412,054 11/1968Milligan et a1 26018 3,461,103 8/1969 Keberle et al. 260-75 FOREIGNPATENTS 1,128,568 9/1968 Great Britain 26029.2 6,614,585 4/1967Netherlands 26029.2

WILLIAM H. SI-IOIRT, Primary Examiner E. H. NIELSEN, Assistant ExaminerUS. Cl. X.R.

156331; 16 1-190; 2609, 29.2 TN, 77.5 AM, 77.5

AQ, 77.5 AX, 77.5 A

